| 主权项 |
1. A measuring device for measuring a process variable, comprising:
an input circuit, having: a line-pair, namely a supply line and a return line, connectable to a superordinated unit, wherein, during operation, energy supply to the measuring device and signal transmission, of an output signal representing the process variable, between the measuring device and the superordinated unit occurs over said line-pair, and wherein, during operation, an input voltage is applied to the measuring device via said line-pair; a series regulator installed in said supply line for controlling an electrical current flowing via said line-pair; a shunt regulator connected after said series regulator and installed in a parallel branch connecting said supply line with said return line; and an apparatus for controlling a voltage drop across said series regulator, wherein:
said apparatus sets the voltage drop across said series regulator as a function of the applied input voltage for input voltages, which are greater than a predetermined minimum input voltage, to a value predetermined by a characteristic curve for a particular input voltage and lying above a minimum value required for operation of said series regulator; a measuring sensor connected to said input circuit and supplied with energy via said input circuit for measuring the process variable; and the predetermined value of the voltage drop for input voltages, which lie above the predetermined minimum input voltage, rises with rising input voltage to a predetermined maximum value. |
